抄録

Experimental results of the transition to turbulence in a constant-acceleration pipe flow were reported in our previous studies where the effects of temporal acceleration on the critical Reynolds number and the propagation of turbulence were investigated in detail. Two patterns of propagation of turbulence were observed: the pattern where the flow transit to turbulence simultaneously and the pattern where the transition propagates downstream. Whereas, square duct flows seems to be different from that of circular duct. There is no paper reported the constant-acceleration square duct flow. In this paper, experimental investigation has been carried out using air as the working fluid to understand the transition to turbulence and critical Reynolds number in constant-acceleration square duct flows. The critical Reynolds number in the high-acceleration regime was compared to an empirical equation proposed originally for the critical Reynolds number in a constant-acceleration pipe flow and existing experimental results.